Some of the identifiers listed above become less problematic if the sample size is large enough so that the potential identifiers could describe several individuals and thus cannot be linked to only one person. Conversely, if the sample size is small, the potential to identify an individual may increase, even in the absence of direct identifiers.

Data may be identifiable if a combination of variables could potentially identify a subject.

HIPAA Privacy Rule Identifiers:18 identifiers specified, most of which are demographic

names

geographic subdivisions smaller than a state

all elements of dates (except year) related to an individual (including dates of admission, discharge, birth, death and, for individuals over 89 years old, the year of birth must not be used)